A common belief is that testosterone deficiency is an “old man’s issue”. This is very wrong. Actually, an excess amount of body fat can cause a man’s testosterone levels to drop as much as 10 years of aging.1 Several studies have demonstrated that too much body fat is associated with reduced testosterone levels independent of aging.2-4

Excess intra-abdominal fat (also known as visceral fat) – a hallmark of the metabolic syndrome - is particularly detrimental, and low levels of both total testosterone and free testosterone are consistent features of men with metabolic syndrome.5 Therefore, it has been suggested that low testosterone levels should be included in the definition of the metabolic syndrome.5

Blood testing of testosterone levels is not part of routine clinical practice. Therefore, it is important that physicians are aware of conditions which indicate that a male patient may have testosterone deficiency and warrant blood testing of testosterone levels.

Abdominal obesity – belly warning

Over the past two decades it has been established beyond any doubt that the amount of fat around the waist (abdominal subcutaneous and visceral fat) is at least as important, if not more important, than the total amount of body fat in predicting and /or causing complications that have been traditionally associated with overweight/obesity.6 Abdominal obesity is a strong risk factor for cardiovascular disease independent of BMI (a proxy for obesity) 7, 8 and is thought to affect disease risk through increased insulin resistance.9, 10 Actually, the common development of insulin resistance with aging is caused by growing bellies, rather than aging per se.11 Notably, normal-weight abdominal obesity is associated with higher mortality than generalized obesity (as defined by BMI).12 An enlarged belly is an especially strong indicator of metabolic risk in men.13, 14 People with a large waist circumference – i.e. those having a belly - have an increased risk of cardiovascular disease, diabetes and cancer, compared to those with smaller waist circumferences, regardless of BMI. 15-19

The association between waist size and testosterone

A commonly used cut-off to “diagnose” abdominal obesity in men is a waist circumference of 40 in (102 cm).

Several studies have shown that belly fat (i.e. abdominal obesity) is inversely associated with testosterone levels in men, i.e. the larger a man’s waist circumference the lower his testosterone level.20-26 The reduction in testosterone with expanding bellies is especially marked for the free “active” testosterone fraction.20, 24, 25 According to the American Heart Association (AHA), the cutoff to diagnose abdominal obesity in men is a waist circumference of 40 in (102 cm).27

A study of 1528 men aged 25-84 years showed how testosterone levels vary by waist circumference, age and BMI (a proxy for obesity).28 Men with a waist of 40 in (102 cm) had a significantly lower total testosterone level compared to men with an optimal waist, defined as 37 in (94 cm) or less, even after adjusting for age and BMI.28 Also, regardless of age, men with larger bellies had a significantly lower free testosterone level. Table 1 summarized how testosterone levels were related to waist in each age group.

Table 1: Total testosterone levels by waist circumference in men aged 25–84 years.28

Waist circumference

Age

94 cm or less

102 cm or more

25-39 40-49 50-59 60-69 70-84

Total testosterone ng/dL (nmol/L)

450 (15.6) 450 (15.6) 415 (14.4) 430 (14.9) 404 (14)

Total testosterone ng/dL (nmol/L)

320 (11.1) 294 (10.2) 320 (11.1) 320 (11.1) 309 (10.7)

25-39 40-49 50-59 60-69 70-84

Free testosterone pg/mL (pmol/L)

105 (302) 93 (268) 77 (221) 68 (196) 59 (171)

Free testosterone pg/mL (pmol/L)

98 (282) 77 (222) 72 (207) 66 (190) 58 (166)

Note that the reference range for total testosterone of the used assay is 200-800, which is why the testosterone levels in the table (especially in young men) may seem low. The difference in total testosterone for a 25-39 year old man with a waist of 94 cm compared to a same age man with a waist of 102 cm is 130 ng/dL with this assay. For analytical assays with wider reference ranges and higher values for the upper end of the reference range, the difference would be larger, possibly in the range of 260-360 ng/dL.

What’s especially notable with this study is that the lowest levels of total and free testosterone were observed in non-obese young men with the highest waist circumference.28

A recent study showed that men over 40 years of age with abdominal obesity have a higher incidence of testosterone deficiency, erectile dysfunction and metabolic syndrome, in proportion to belly size.29 This study found that a large belly can reduce testosterone levels by half.29

The waist-to-height ratio as an indicator of cardiometabolic risk

Increasing evidence shows that indexing waist circumference to height, as the waist-to-height ratio, is a valuable yet simple indicator to assess health risks. The waist-to-height ratio is still a relatively unknown measure, even though the first studies showing that it is an easy and useful predictor of heart disease risk factors were published in the 1990s.30-36

The waist-to-height ratio is the best simple indicator of cardiovascular risk and mortality, followed by waist circumference and waist-to-hip ratio.37 The previously popular BMI is inferior and should not be used for assessment of health risk.37

When comparing waist circumference alone with the waist-to-height ratio, the waist-to-height ratio is a significantly better indicator for cardiovascular disease risk, dyslipidemia (cholesterol and blood fat abnormalities), diabetes and high blood pressure, in both men and women, regardless of age and ethnic group.38 This finding comes from a meta-analysis of studies involving more than 300,000 adults in several ethnic groups.38

The waist-to-height ratio and life expectancy

The waist-to-height ratio also gives an idea about how body shape can affect life expectancy. The Health and Lifestyle Survey (HALS) is a prospective study of health and behavior, based on a representative sample of the British population (England, Wales and Scotland).39 Table 2 shows results from 20-years of follow-up.

Table 2: Effect of the waist-to-height ratio on life expectancy. Numbers represent years of life lost.39

WHtR

30 year old

50 year old

70 year old

Man

Woman

Man

Woman

Man

Woman

0.5

0

0.1

0

0.1

0

0

0.6

1.7

1.4

1.4

1.4

0.5

0.8

0.7

7.2

4.6

5.8

4.1

2.9

2.7

over 0.8

20.2

10.6

14.3

9.2

6.7

5.9

WHtR: waist-to-height ratio

As shown in table 2, for a 30 year old man and woman, a high waist-to-height ratio over 0.8 can shorten life by as much as 20 and 10 years, respectively. For a 50 year old man and woman, a waist-to-height ratio of 0.7 may shorten life by 14 and 9 years, respectively. This study shows that body shape can have serious consequences far beyond mere physical attractiveness.

To find out your waist-to-height ratio, measure your waist at the level of the navel and divide by your height. You can use either inches or centimeters (as long as waist and height are expressed using the same unit). A waist-to-height ratio below 0.5 is considered ideal. This translates into the health message “keep your waist circumference to less than half your height.” 40 Table 3 shows how to do the calculation for a representative man and woman, and how to interpret the risk thresholds.

Table 3: How to calculate your waist-to-height ratio, and effect of “waist loss” on the waist-to-height ratio.

Man

Woman

Waist

102 cm

89 cm

Height

178 cm

163 cm

Waist-to-height ratio

102 / 178 = 0.57

89 / 163 = 0.55

Effect of “waist loss” - by exercise and improved food habits - on the waist-to-height ratio:

Waist

89 cm

81 cm

New waist-to-height ratio

89 / 178 = 0.5

81 / 163 = 0.5

The waist measures in table 3 – (102 cm for the man and 89 cm for the woman - are the cutoffs for abdominal obesity, according to the American Heart Association (AHA).27 As shown in the table, this is above 0.5 for a man/woman of average height.

How to interpret the waist-to-height ratio value

As stated above, a waist-to-height ratio below 0.5 is considered ideal. A more detailed interpretation of waist-to-height ratio values is given in table 4.

Table 4: Interpretation of waist-to-height ratio values.

Waist-to-height ratio

Body shape (see illustration below)

Comment

below 0.4

you are a chili pepper

0.45

you are a healthy pear

0.5 to 0.6

you are a pear-apple

You have more fat around your waist than is healthy. Exercise more and chose better food options. A value close to 0.6 may indicate that you have testosterone deficiency.28, 41 Ask your doctor to check your testosterone level.

above 0.61

you are an unhealthy apple

The fat around your waist is damaging your health and shortening your life expectancy.39 You need to start exercising and eating healthier. You likely have testosterone deficiency.28, 41 Tell your doctor you want to have your testosterone level checked.

To give an idea about body shapes for different waist-to-height ratios, the illustration in figure 2 shows typical body shapes for a range of waist-to-height ratio values.

Figure 4: Approximate waist-to-height ratios for typical body shapes.

Look up your waist-height ratio using the Ashwell Shape Chart®

One can also easily look up the waist-to-height ratio “danger zone” in the Ashwell Shape Chart®, figure 5. Just locate the waist and height numbers and see what zone they fall in. The Ashwell Shape Chart® also shows how much waist needs to be reduced in order to move into a patient into a healthier zone.

Why divide waist by height?

The waist-to-height ratio is a better proxy of intra-abdominal (belly) fat - and thus health risk - than waist circumference alone, because of the correlations between waist circumference, height, and intra-abdominal fat.32 For a given waist circumference, shorter people have more dangerous abdominal fat and associated cardiovascular risk factors than taller people.42 This is why the waist-to-height ratio is a better indicator of your health status than your waist alone.

Applies to everybody, regardless of sex and ethnicity

Aside being the most accurate indicator of health risk, the waist-to-height ratio applies equally to men and women, children as well as young and older adults, and in all ethnic populations.43, 44 This makes the waist-to-height ratio unique as a health screening tool. Both waist circumference and BMI have sex and ethnic specific cut-offs, which complicates their practical use.43, 45

It has therefore been proposed that the waist-to-height ratio should be used (instead of waist circumference) as part of diagnosing the metabolic syndrome.38, 45 Hopefully the next revision of clinical guidelines on the assessment of cardio-metabolic risk will give the waist-to-height ratio the attention it deserves. There is a burning need for education and action to improve preventive medicine efforts worldwide by educating primary care physicians as well as the general population and patients at risk about the dangers of abdominal obesity and of waist-to-height ratio as an easy, reliable way to assess cardio-metabolic risk.43, 45, 46

The waist-to-height ratio as a tool to screen for testosterone deficiency

A study was conducted to specifically examine the utility of waist-to-height ratio for prediction of testosterone levels. 207 men aged 54–86 years were recruited on the basis of having symptoms indicative of testosterone deficiency, but who were otherwise in good health.41 This is the first study to show that adjusting waist circumference for height (i.e. the waist-to-height ratio) improves prediction of both total and free testosterone levels, compared with either waist alone or BMI, even after adjustment for age. The correlation of the waist-to-height ratio with total testosterone levels was stronger than that of free testosterone levels (figure 6).

Figure 6: Correlation between the waist-to-height ratio and total and free testosterone levels.41

A moderate to high AMS score combined with a waist-to-height ratio of 0.5 or higher is a strong indication for blood testing of testosterone levels.

Effect of testosterone therapy on the waist-to-height ratio

Considering that a waist-to-height ratio above 0.5 is associated with reduced testosterone levels 41, and that testosterone therapy reduces belly fat 47-49, then testosterone therapy should reduce the waist-to-height ratio.

A recent study investigated the effect of testosterone therapy on changes in body fat measures, including the waist-to-height ratio.50 In an observational, prospective registry study of 656 men (mean age of 61 years) with total testosterone levels below 349 ng/dL (≤ 12.1 nmol/L) and symptoms of hypogonadism, 360 men were treated with testosterone undecanoate injections 1000 mg/12 weeks (following an initial 6-week interval) for up to 10 years. The other 296 men did not receive testosterone treatment and served as controls. Measurements were taken at least twice a year, and 8-year data were analyzed. As shown in table 3, baseline waist-to-height ratio was 0.6 with a corresponding testosterone level of 284 ng/dL (9.84 nmol/L).

Table 3: Baseline and changes in waist-to-height ratio and testosterone levels during 8 years of testosterone therapy with testosterone undecanoate.50

Waist-to-height ratio

Total testosterone level

ng/dL (nmol/L)

Baseline (year 0)

0.6

284 (9.84)

Year 1

0.59

465 (16.13)

Year 2

0.57

495 (17.15)

Year 3

0.57

486 (16.85)

Year 4

0.56

497 (17.23)

Year 5

0.56

496 (17.19)

Year 6

0.56

473 (16.4)

Year 7

0.55

479 (16.59)

Year 8

0.55

477 (16.53)

After 8 years of testosterone treatment, the waist-to-height ratio had dropped to 0.55 and the testosterone level had increased to 477 ng/dL. Figure 7 graphically illustrates the yearly changes in the waist-to-height ratio.

Summary

While relatively unknown among healthcare professionals, it is now well documented in the medical research literature that expanding bellies are associated with reduced testosterone levels in men, and that testosterone treatment reduces belly fat.

Because blood testing of testosterone levels is not part of routine clinical practice, physicians need to be aware of conditions that are associated with testosterone deficiency. The waist-to-height ratio, combined with assessment of symptoms/sign, can provide two strong indications for blood testing of testosterone levels.